1. Field of the Invention
The present invention relates to an exhaust gas post processing system that raises the temperature of the exhaust gas at an early stage of the engine operating and prevents the temperature of the exhaust gas from being excessively raised.
2. Description of Related Art
Generally, so as to purify the exhaust gas of the diesel vehicle, a diesel oxidation catalyst (DOC) and a diesel particulate filter (Diesel particulate filter) are applied and the DOC oxidizes a carbon monoxide and a hydrocarbon to eliminate them.
Further, the diesel particulate filter traps particulate matters of the exhaust gas, if the trapped PM exceeds a predetermined value, a fuel is post injected, the temperature of the exhaust gas is raised by the fuel oxidation heat in the DOC, and the trapped PM is burned in the diesel particulate filter.
Meanwhile, there is a problem that the exhaust gas purification catalyst (DOC, DPF, LNT, HC-SCR, and so on) is not activated from a low temperature of the exhaust gas in a condition that the engine is in an early stage of the operating. In addition, there is a problem that the catalyst is over heated by the exhaust gas passing the catalyst.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.